This is an initial two-year study with three one-year options, which means that the contract may run through 8/31/94. The purpose of this contract is to have IARC conduct international epidemiologic studies of occupational and environmental cancers. The current contract calls for two tasks to be performed. Task I will be for the maintenance and analyses of the International Register of persons exposed to Phenoxy Acid Herbicides and Contaminants, and to carry out studies of cancer mortality and the incidence in persons exposed to these agents. The main aim is to assess qualitatively and quantitatively the cancer risk from exposure to phenoxy acid herbicides and their contaminants, notably TCDD. The purpose of Task II is to investigate cancer risk among nuclear industry workers by combined analysis of data from existing studies and carrying out an international collaborative study of workers in facilities not yet studied. In the first phase the feasibility of such a study will be investigated. The main aim of the proposed studies is to obtain more precise estimates of the carcinogenic risk induced by chronic low dose exposures to ionizing radiation.